Résumé
Soil fauna is a key control of the decomposition rate of leaf litter, yet its interactions with litter quality and the soil environment remain elusive. We conducted a litter decomposition experiment across different topographic levels within the landscape replicated in two rainforest sites providing natural gradients in soil fertility to test the hypothesis that low nutrient availability in litter and soil increases the strength of fauna control over litter decomposition. We crossed these data with a large dataset of 44 variables characterizing the biotic and abiotic microenvironment of each sampling point and found that microbe-driven carbon (C) and nitrogen (N) losses from leaf litter were 10.1 and 17.9% lower, respectively, in the nutrient-poorest site, but this among-site difference was equalized when meso- and macrofauna had access to the litterbags. Further, on average, soil fauna enhanced the rate of litter decomposition by 22.6%, and this contribution consistently increased as nutrient availability in the microenvironment declined. Our results indicate that nutrient scarcity increases the importance of soil fauna on C and N cycling in tropical rainforests. Further, soil fauna is able to equalize differences in microbial decomposition potential, thus buffering to a remarkable extent nutrient shortages at an ecosystem level.
Auteurs, date et publication :
Auteurs Guille Peguero , Jordi Sardans , Dolores Asensio , Marcos Fernández-Martínez , Albert Gargallo-Garriga , Oriol Grau , Joan Llusià , Olga Margalef , Laura Márquez , Romà Ogaya , Ifigenia Urbina , Elodie A. Courtois , Clément Stahl , Leandro Van Langenhove , Lore T. Verryckt , Andreas Richter , Ivan A. Janssens , Josep Peñuelas
Publication : Proceedings of the Royal Society B: Biological Sciences
Date : 2019
Volume : 286
Issue : 1910
Pages : 20191300
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Objectives: Carbon fixed during photosynthesis is exported from leaves towards sink organs as non-structural carbohydrates (NSC), that are a key energy source for metabolic processes in trees. In xylem, NSC are mostly stored as soluble sugars and starch in radial and axial parenchyma. The multi-functional nature of xylem means that cells possess several functions, including water transport, storage and mechanical support. Little is known about how NSC impacts xylem multi-functionality, nor how NSC vary among species and climates. We collected leaves, stem and root xylem from tree species growing in three climates and estimated NSC in each organ. We also measured xylem traits linked to hydraulic and mechanical functioning. Data description: The paper describes functional traits in leaves, stems and roots, including NSC, carbon, nitrogen, specific leaf area, stem and root wood density and xylem traits. Data are provided for up to 90 angiosperm species from temperate, Mediterranean and tropical climates. These data are useful for understanding the trade-offs in resource allocation from a whole-plant perspective, and to better quantify xylem structure and function related to water transportation, mechanical support and storage. Data will also give researchers keys to understanding the ability of trees to adjust to a changing climate.
Auteurs, date et publication :
Auteurs Guangqi Zhang , Pascale Maillard , Zhun Mao , Loic Brancheriau , Julien Engel , Bastien Gérard , Claire Fortunel , Jean Luc Maeght , Jordi Martínez-Vilalta , Merlin Ramel , Sophie Nourissier-Mountou , Stéphane Fourtier , Alexia Stokes
Publication : BMC Research Notes
Date : 2025
Volume : 15
Issue : 1
Pages : 1–4
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Non-structural carbohydrates (NSC) are considered as indicators of the balance between tree carbon sources and sinks and reflect functional strategies throughout different biomes. However, little is known about the contribution of NSC to tree economics, and in particular, whether leaf, stem and coarse root traits co-ordinate together into a whole-tree economics spectrum. Twenty-four functional traits (including NSC content) were measured in leaves, stem and coarse root xylem of up to 90 angiosperm tree species in temperate, Mediterranean and tropical climates. By performing principal component analysis and standardized major axis regression, we explored the relationships between NSC and other functional traits, as well as the effects of climate and phylogeny on these relationships. Our results revealed a covariation between leaf and coarse root NSC content and leaf economic traits, whereas stem NSC content was largely decoupled from the leaf economics spectrum that was mostly driven by leaf nitrogen content and leaf mass per area. Coarse root xylem traits were closely correlated with leaf traits, while most stem xylem traits were independent from the leaf economics spectrum but covaried with coarse root traits. Trade-offs among traits in tropical species opposed those from other climates. Evolutionary history affected relationships among certain traits but did not change overall patterns. We conclude that due to leaf habit, an extended growing season and heightened defences, tropical species form distinct conservative resource acquisition strategies. Across all climates, as the stem must provide an efficient transport route between roots and leaves, while maintaining the display of branch and leaf organs, stem xylem design and NSC storage capacity lead to a stem economics spectrum that is largely independent from the leaf spectrum, but is coupled with that of coarse roots due to anatomical continuity. Read the free Plain Language Summary for this article on the Journal blog.
Auteurs, date et publication :
Auteurs Guangqi Zhang , Zhun Mao , Pascale Maillard , Loïc Brancheriau , Bastien Gérard , Julien Engel , Claire Fortunel , Patrick Heuret , Jean Luc Maeght , Jordi Martínez-Vilalta , Alexia Stokes
Publication : Functional Ecology
Date : 2025
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Sandra Barantal , Heidy Schimann , Nathalie Fromin , Stephan Hättenschwiler
Publication : Ecosystems
Date : 2012
Volume : 15
Issue : 7
Pages : 1039–1052
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Benjamin Brede , Louise Terryn , Nicolas Barbier , Harm M Bartholomeus , Renée Bartolo , Kim Calders , Géraldine Derroire , Sruthi Krishna Moorthy , Alvaro Lau , Shaun R Levick , Pasi Raumonen , Hans Verbeeck , Di Wang , Tim Whiteside , Jens Van Der Zee , Martin Herold
Publication : Remote Sensing of Environment
Date : 2025
Volume : 280
Issue : July
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes.
Auteurs, date et publication :
Auteurs Julie Bossu , Jacques Beauchêne , Yannick Estevez , Christophe Duplais , Bruno Clair , Warren Batchelor
Publication : Plos One
Date : 2016
Volume : 11
Issue : 3
Pages : e0150777
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Knowledge of the wood properties of tropical tree species is still relatively limited, making that timber exploitation focuses on a few abundant, large-diameter species. Very few is known about small diameter trees although they may be used, directly as round wood, in construction timber building. The aim of this work was to determine the wood natural durability of 8 candidate species for roundwood building in French Guiana ; Oxandra askeckii, Goupia glabra, Lecythis persistens, Hymenopus heteromorphus, Pouteria bangii, Licania alba, Tachigali melinonii, Simarouba amara and Virola surinamensis wood samples were exposed to white rots (European and tropical), brown rot (European) and European subterranean termites (using non-choice and multi-choice tests), in laboratory conditions by screening tests adapted from European standards.
Auteurs, date et publication :
Auteurs Maëva Leroy , Kévin Candelier , Jérémie Damay , Julie Bossu , Romain Lehnebach , Marie-France Thevenon , Jacques Beauchene , Bruno Clair
Date : 1970
Catégorie(s)
#⛔ No DOI found #CIRAD #FORET ParacouRésumé
Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5–7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.
Auteurs, date et publication :
Auteurs Camille S. Delavaux , Thomas W. Crowther , Constantin M. Zohner , Niamh M. Robmann , Thomas Lauber , Johan van den Hoogen , Sara Kuebbing , Jingjing Liang , Sergio De-Miguel , Gert Jan Nabuurs , Peter B. Reich , Meinrad Abegg , Yves C. Adou Yao , Giorgio Alberti , Angelica M. Almeyda Zambrano , Braulio Vilchez Alvarado , Esteban Alvarez-Dávila , Patricia Alvarez-Loayza , Luciana F. Alves , Christian Ammer
Publication : Nature
Date : 2025
Volume : 621
Issue : November 2022
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Leaf area is a key structural characteristic of forest canopies because of the role of leaves in controlling many biological and physical processes occurring at the biosphere-atmosphere transition. High pulse density Airborne Laser Scanning (ALS) holds promise to provide spatially resolved and accurate estimates of plant area density (PAD) in forested landscapes, a key step in understanding forest functioning: phenology, carbon uptake, transpiration, radiative balance etc. Inconsistencies between different ALS sensors is a barrier to generating globally harmonised PAD estimates. The basic assumption on which PAD estimation is based is that light attenuation is proportional to vegetation area density. This study shows that the recorded extinction strongly depends on target detectability which is influenced by laser characteristics (power, sensitivity, wavelength). Three different airborne laser scanners were flown over a wet tropical forest at the Paracou research station in French Guiana. Different sensors, flight heights and transmitted power levels were compared. Light attenuation was retrieved with an open source ray-tracing code (http://amapvox.org). Direct comparison revealed marked differences (up-to 25% difference in profile-averaged light attenuation rate and 50% difference at particular heights) that could only be explained by differences in scanner characteristics. We show how bias which may occur under various acquisition conditions can generally be mitigated by a sensor intercalibration. Alignment of light weight lidar attenuation profiles to ALS reference attenuation profiles is not always satisfactory and we discuss what are the likely sources of discrepancies. Neglecting the dependency of apparent light attenuation on scanner properties may lead to biases in estimated vegetation density commensurate to those affecting light attenuation estimates. Applying intercalibration procedures supports estimation of plant area density independent of acquisition characteristics.
Auteurs, date et publication :
Auteurs Grégoire Vincent , Philippe Verley , Benjamin Brede , Guillaume Delaitre , Eliott Maurent , James Ball , Ilona Clocher , Nicolas Barbier
Publication : Remote Sensing of Environment
Date : 2023
Volume : 286
Issue : December 2022
Pages : 113442
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The purpose of this paper is twofold, considering first the generalization of a multichannel speckle filter in order to handle temporal stacks of polarimetric SLC SAR data, and secondly the development of an ad hoc performance indicator based on the Polarimetric Orientation Angle (POA) in order to better estimate the resulting speckle reduction than the standard Equivalent Number of Looks (ENL) over densely vegetated regions, like tropical forests. Being based on the ability of PolSAR measurements to retrieve ground slopes through dense vegetation, this performance indicator requires the use of low frequencies such as P-band, as well as fully polarimetric data. This study has thereby a particular interest in the context of the upcoming BIOMASS spaceborne mission whose launch is scheduled in 2023, and makes use of data from the TropiSAR airborne campaign initiated in the early stage of the mission developments. Conducted over several test sites of tropical dense forests in French Guiana, this campaign gives us the opportunity herein to exploit P-band temporal stacks with repeated time intervals transposable to BIOMASS in terms of signal decorrelation. The application of the generalized multichannel speckle filter to the Paracou test site dataset reveals the limitations of the standard ENL analytical formula to assess speckle reduction in the case of spatially correlated media like dense forests, and for this purpose the interest of the correlation between POA and azimuthal slopes computed from an independent Digital Surface Model.
Auteurs, date et publication :
Auteurs Colette Gelas , Ludovic Villard , Laurent Ferro-Famil , Laurent Polidori , Thierry Koleck , Sandrine Daniel
Publication : Remote Sensing
Date : 2021
Volume : 13
Issue : 1
Pages : 142